Food Chemistry

5.3 Individual Aroma Compounds 381

Table 5.30.Odor thresholds of esters

Compound Odor
threshold
(μg/kg,
water)

Methylpropionic acid methyl ester 7
2-Methylbutyric acid methyl ester 0. 25
Methylpropionic acid ethyl ester 0. 1
(S)-2-Methylbutyric acid ethyl ester 0. 06
Butyric acid ethyl ester 0. 1
Isobutyric acid ethyl ester 0. 02
3-Methylbutyric acid ethyl ester 0. 03
Caproic acid ethyl ester 5
Cyclohexanoic acid ethyl ester 0. 001
(R)-3-Hydroxyhexanoic ethyl ester 270
Caprylic acid ethyl ester 0. 1
(E,Z)-2,4-Decadienoic acid ethyl ester 100
trans-Cinnamic acid ethyl ester 0. 06
Benzoic acid ethyl ester 60
Salicylic acid methyl ester 40
Butyl acetate 58
2-Methylbutyl acetate 5
3-Methylbutyl acetate 3
Pentyl acetate 38
Hexyl acetate 101
(Z)-3-Hexenyl acetate 7. 8
Octyl acetate 12
2-Phenylethyl acetate 20

Table 5.31.Lactones in food

Name Structure Aroma quality Occurrence

4-Nonanolide Reminiscent Fat-containing food,
(γ-nonalactone) of coconut oil, fatty crispbread, peaches

4-Decanolide Fruity, peaches Fat-containing food,
(γ-decalactone) cf. Table 5.13

5-Decanolide Oily, peaches Fat-containing food,
(δ-decalactone) cf. Table 5.13

(Z)-6-Dodecen- Sweet Milk fat, peaches
γ-lactone

3-Methyl-4- Coconut-like Alcoholic
octanolide (whisky- beverages
or quercus lactone)

that the precursors oleic and linoleic acid are

regio- and stereospecifically oxidized to hy-

droxy acids (Fig. 5.30), which are shortened by

β-oxidation and cyclized to lactones. The indi-

vidual steps in the biosynthesis are represented in

Fig. 5.31 using (R)-δ-decalactone, a key odorant

of butter (cf. 10.3.4).

Linoleic acid is metabolized by cows with the for-

mation of (Z)-6-dodecen-γ-lactone as a secondary

product (Fig. 5.30). Its sweetish odor enhances

the aroma of butter. On the other hand, it is un-

desirable in meat.

Table 5.32.Odor thresholds of lactones

Compound Odor threshold

(μg/kg, water)

γ-Lactones

γ-Hexalactone 1600

γ-Heptalactone 400

γ-Octalactone 7

γ-Nonalactone 30–65

γ-Decalactone 11

γ-Dodecalactone 7

δ-Lactones

δ-Octalactone 400

δ-Decalactone 100

6-Pentyl-α-pyrone 150